As high as the violent crime rate is in gun-outlawing Massachusetts (457 per 100,000 people), it is significantly lower than many gun-friendly states like Alaska (633), Arkansas (508), Florida (612), Louisiana (620), Missouri (492), Neveda (702), New Mexico (619), Oklahoma (501), South Carolina (671), Tennessee (668), and Texas (491).
My point is that you can’t draw the conclusion that have drawn from the statistic that you cite. When you look at the stats for all states, you will find that some gun-hating states have high violent crime rates and some have very low violent crime rates. The same can be said about the gun-loving states. I suspect that the violent crime rate has more to do with demographics, than gun laws.
A quick wild guess analysis to explain would be that Alaska has more men than women, the several southern states have more illegals, and the others might be related to education levels. That ought to get someone mad. Sorry in advance, total speculation. Demographics probably drive the numbers more than gun laws, but that said I think the correlation I'd be interested in is the per capita rate of concealed carry to violent crime.